In the paper converting field and in other industrial sectors machines are known to produce rolls of web material starting from reels of large diameter, which are unwound in specific unwinding machines that feed winding or rewinding machines. These latter wind the web material to form rolls of diametrical dimensions equal to the dimensions of the product destined for consumption. These rolls present, in some cases, an axial extension which is a multiple of the length of the rolls destined for consumption, and are therefore subsequently cut to transform the rolls or logs produced by the rewinding machines into individual rolls or small rolls of lower diameter for packaging and marketing.
These rolls are usually formed through winding around a tubular winding core, typically made of cardboard or plastic. The winding core remains inside the finished product. US-A-2005/0279875 and other documents of the same patent family describe a rewinding machine particularly designed for producing tissue paper rolls around winding cores.
In other cases the rolls are wound around removable spindles, that are extracted from the roll or log once this latter has been finished and unloaded from the rewinding machine. U.S. Pat. No. 6,565,033 and U.S. Pat. No. 6,752,345 describe a winding system with removable spindle.
Also machines have been provided for producing logs or rolls of web material, typically tissue paper, without winding spindle or core. U.S. Pat. Nos. 5,538,199; 5,603,467; 5,639,046; 5,690,296; US-A-2009/0101748 describe examples of this machine type.
The machine described in U.S. Pat. No. 5,639,046 comprises for instance: a path for feeding the web material; a first winding roller and a second winding roller defining a nip across which the web material passes; downstream of the nip, a third winding roller with a movable axis cooperating with the first winding roller and with the second winding roller to form a winding cradle for said rolls and, upstream of the nip, a surface delimiting a channel for forming the first winding turns of each roll.
This winding technique has several advantages if compared with the traditional systems for winding around winding cores or spindles, and also if compared with the systems for winding around removable spindles. In particular, with the same outer diameter, the rolls formed without winding core or spindle have a greater quantity of wound web material, i.e. they have, with the same quantity of wound material, a lower bulk. The storage and transport costs are thus reduced. As there is no need for a winding core, there is consequently no need in the production line for a machine for producing the winding cores, a so-called core winder. This leads to a greater ease in the line arrangement, to space-saving and to a reduction in the labor costs for managing the production line. Also the production costs decrease, as there is no more consumption of cardboard and glue necessary for producing the tubular winding cores.
If compared with the winding systems with removable spindle, the winding systems without spindle and without tubular core do not require complex mechanisms for removing and recycling the winding spindles.